Am a bit lost, so hopefully I can get some good advice here.
we're developing a multi-tier .Net app; my thoughts are to automate testing of the business rules tier (thus making testing of the business rules UI-independent).
I believe I should be able to do this using API testing, to exercise the methods of the relevant .Net components (written in C#)
as I understand it, I shouldn't need access to the source code to do this; I should be able to call methods from my code just using APIs. Question: how is this done? What are the nuts and bolts of doing this?
eg, if I'm using the Visual Studio IDE, what code would I write to access one of the application's APIs?
Well you need to have a reference to the DLLs or objects you are testing as well as the API documentation for how to call the API.
Have you ever added a reference into VS before?
Think of it this way, if you add a COM reference to the Microsoft Excel Interop you now have access to all the different public APIs such as opening and closing the Excel object, opening spreadsheets, reading and writing data, etc...
You need to figure out (use your dev team) what reference you need to make from VS to get access to the APIs then ask them for the API documentation so you know how to make the calls and what kind of data and var structure they require and return.
If this or any response has helped you, please reply to the thread stating that it worked so other people with a similar issue will know how you fixed your issue!